Continuity mistake: When Julie is being dragged by Freddy on the ceiling you see traces of blood where she has been dragged. But there is also blood in front of her where she hasn't been dragged yet. (01:18:05)
Visible crew/equipment: After Julie is killed, she falls to the floor, and if you look closely you can see the big black mattress she lands on. (Seen on DVD version.) (01:18:35)
Continuity mistake: When Freddy cuts through the sheet before entering reality you see him making a large cut in the sheet. On the next shot, the sheet is only cut in face level. (01:23:50)
Continuity mistake: Heather follows the sleeping pills (bread crumbs) into Dylan's room. She has the pills in her right hand and the kitchen knife in the left. She picks up two pills then reaches for the one on the pillow. She reaches for it with her index finger and thumb her hand closed but when they show the close up on her hand she picks it up with her middle finger and thumb with her hand open. (01:27:20)
Continuity mistake: Towards the end of the film Nancy takes a big kitchen knife to fight Freddy with. When she is falling into Freddy's lair from her son's bed, she clearly has nothing in her hands. However, as she emerges from the water she has fallen in, the knife appears in her left hand. (01:29:10)
Continuity mistake: When Freddy is reaching for Dylan inside the fireplace, his left hand changes position on the bars. (01:34:15)
Continuity mistake: When Nancy is covered with Freddy's tongue, the tongue goes under her shirt. When it cuts, the tongue no longer is under the shirt. (01:36:20)
Continuity mistake: When Dylan and Heather are looking at the manuscript you see them looking at the first page. In the next shot she flips back to the first page again. (01:38:50)
Visible crew/equipment: In the playground scene, when Dylan jumps from the top of the rocket, it's an adult stunt double.
Continuity mistake: Julie punches a nurse and she passes out on the floor. She closes the door and locks it. Next scene shows the same nurse outside the door trying to get in.
Chosen answer: Mostly just very subtle hints. In the beginning when she arrives right around the same time that Heather gets a call from the psycho-stalker, suggesting a possible connection. And the fact she's alone with Dylan many times during the film, as she could be subtly manipulating him to act out.
In the final version of the movie, Julie is not connected to Freddy in any way, and she was certainly not manipulating Dylan, nor anyone else. The fact that she arrives right around at the same time that Heather gets mysterious call is a pure coincidence.